KVPY SX SB Exam 2013 Question Paper

Question : 109 of 120

Marks: +1, -0

The amount of

\Na_2\S_2\O_ 3 . 5\H_2\O

required to completely reduce 100 mL of 0.25 N iodine solution, is

Solution:

N_1V_1 = N_2V_2

mili eq. of hypo = 0.25 × 100
mili eq. of hypo= 25
eq. of hypo = 0.025
mole of hypo = 0.025 × 1

(∵ \V_f = 1)

weight of hypo = 0.025 × 248 = 6.2 g

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